Self-contained space heaters of one type or another have been around for many years, some fired by kerosene or other liquid fuels, others by natural gas or propane and still others electrically. Many such heaters are portable and can be used anywhere from a duck blind to the living room. Those using natural gas or electricity are, of course, confined in their applications to where such sources of fuel and power are available.
One distinct advantage of the electrically-heated units is that they do not require venting and, therefore, are considered much safer than those which emit fumes or even require oxygen for combustion. Many such heaters are used as a supplementary, as opposed to a primary, source of heat, the main source being a hot air or hot water furnace.
There are several factors that should be considered in purchasing a small space heater in addition to the primary one of BTU output per unit of fuel, be it a combustible liquid or gas or energy in the form of electricity. Among these are, of course, safety, portability, initial cost, appearance, heat-up time and versatility.